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Abc of antenatal care1

  1. 1. ABC OFANTENATAL CARE Fourth editionGeoffrey Chamberlain and Margery Morgan
  2. 2. ABC OF ANTENATAL CARE Fourth edition GEOFFREY CHAMBERLAIN Professor Emeritus, Department of Obstetrics and Gynaecology, St George’s Hospital Medical School, London and Consultant Obstetrician, Singleton Hospital, Swansea and MARGERY MORGANConsultant Obstetrician and Gynaecologist, Singleton Hospital, Swansea
  3. 3. © BMJ Books 2002 BMJ Books is an imprint of the BMJ Publishing GroupAll rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording and/or otherwise, without the prior written permission of the publishers First published in 1992 Second edition 1994 Third edition 1997 Fourth edition 2002 by BMJ Books, BMA House, Tavistock Square, London WC1H 9JR British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library ISBN 0-7279-1692-0 Cover image depicts body contour map of a pregnant woman at 36 weeks. With permission from Dr. Robin Williams/ Science Photo Library. Typeset by Newgen Imaging Systems Pvt Ltd. Printed and bound in Spain by GraphyCems, Navarra
  4. 4. Contents Preface iv 1. Organisation of antenatal care 1 2. The changing body in pregnancy 5 3. Normal antenatal management 9 4. Checking for fetal wellbeing 17 5. Detection and management of congenital abnormalities 24 6. Work in pregnancy 31 7. Vaginal bleeding in early pregnancy 36 8. Antenatal medical and surgical problems 43 9. Raised blood pressure in pregnancy 5510. Antepartum haemorrhage 6111. Small for gestational age 6612. Preterm labour 7213. Multiple pregnancy 7814. The audit of birth 84 L’envoi 88 Index 89 iii
  5. 5. PrefaceThe chapters in this book appeared originally as articles in the British Medical Journal and were welcomed by practitioners. Thearticles were retuned for publication as a book, the first edition appearing in 1992. Demand asked for more and so the book wasupdated for a second, a third and now a fourth edition in 2002. Antenatal care has evolved from a philanthropic service for mothers and their unborn babies to a multiphasic screeningprogramme. Much has been added in the past few years but a lack of scientific scrutiny has meant that little has been taken away.Healthy mothers and fetuses need little high technological care but some screening is desirable to allocate them with confidence tothe healthy group of pregnant women. Women and fetuses at high risk need all the scientific help available to ensure the safestenvironment for delivery and aftercare. The detection and successful management of women and fetuses at high risk is the scienceof antenatal care; the care of other mothers at lower risk is the art of the subject and probably can proceed without much technology.Midwives are practitioners of normal obstetrics and are taking over much of the care of normal or low-risk pregnancies, backed upby general practitioner obstetricians in the community and by consultant led obstetric teams in hospitals. This book has evolved from over 40 years of practice, reading, and research. We have tried to unwind the tangled skeins ofaetiology and cause and the rational from traditional management, but naturally what remains is an opinion. To broaden this, theauthorship has been widened; Dr Margery Morgan, a consultant obstetrician and gynaecologist at Singleton Hospital, has joinedProfessor Chamberlain as a co-author, bringing with her the new skills used in antenatal care. We thank our staff at Singleton Hospital for willingly giving good advice and contributing to this book, especially HowardWhitehead, medical photographer, and Judith Biss, ultrasonographer. Our secretaries Caron McColl and Sally Rowland diligentlydecoded our writings and made the script legible while the staff of BMJ Books, headed by Christina Karaviotis, turned the whole intoa fine book. Geoffrey Chamberlain Margery Morgan Singleton Hospital Swanseaiv
  6. 6. 1 Organisation of antenatal careLooking after pregnant women presents one of the paradoxesof modern medicine. Normal women proceeding through anuneventful pregnancy require little formal medicine.Conversely, those at high risk of damage to their own health orthat of their fetus require the use of appropriate scientifictechnology. Accordingly, there are two classes of women, thelarger group requiring support but not much intervention andthe other needing the full range of diagnostic and therapeuticmeasures as in any other branch of medicine. To distinguishbetween the two is the aim of a well run antenatal service. Antenatal clinics provide a multiphasic screening service;the earlier women are screened to identify those at high risk ofspecified problems the sooner appropriate diagnostic tests canbe used to assess such women and their fetuses and treatmentcan be started. As always in medicine, diagnosis must precedetreatment, for unless the women who require treatment can beidentified specifically, management cannot be correctlyapplied.BackgroundSome women attend for antenatal care because it is expectedof them. They have been brought up to believe that antenatalcare is the best way of looking after themselves and theirunborn children. This is reinforced in all educational sourcesfrom medical textbooks to women’s magazines. Prenatal care started in Edinburgh at the turn of the 20th Figure 1.1 New mother and her babycentury, but clinics for the checking of apparently wellpregnant women were rare before the first world war. Duringthe 1920s a few midwifery departments of hospitals andinterested general practitioners saw women at intervals tocheck their urine for protein. Some palpated the abdomen, butmost pregnant women had only a medical or midwiferyconsultation once before labour, when they booked. Otherwise,doctors were concerned with antenatal care only “if any of thecomplications of pregnancy should be noticed”. Obstetrics andmidwifery were first aid services concerned with labour and itscomplications: virtually all vigilance, thought, and attentioncentred on delivery and its mechanical enhancement. Littleattention was paid to the antenatal months. During the 1920s a wider recognition emerged of thematernal problems of pregnancy as well as those of labour; themedical profession and the then Ministry of Health woke up torealise that events of labour had their precursors in pregnancy.Janet Campbell, one of the most farsighted and clear thinkingwomen in medicine, started a national system of antenatalclinics with a uniform pattern of visits and procedures; herpattern of management can still be recognised today in all the Figure 1.2 Dame Janet Campbellclinics of the Western world. Campbell’s ideas became the clinical obstetric screeningservice of the 1930s. To it has been added a series of tests, oftenwith more enthusiasm than scientific justification; over theyears few investigations have been taken away, merely moreadded. Catalysed by the National Perinatal EpidemiologicalUnit in Oxford, various groups of more thoughtfulobstetricians have tried to sort out which of the tests are in factuseful in predicting fetal and maternal hazards and which havea low return for effort. When this has been done a rationalantenatal service may be developed, but until then we mustwork with a confused service that “growed like Topsy”. It is amixture of the traditional clinical laying on of hands and a 1
  7. 7. ABC of Antenatal Care 100 80% Uptake of antenatal care 60 First Second 40 World World War War 20 Figure 1.4 Antenatal clinics evolved from child welfare clinics, producing a prenatal version of the infant clinics 0 1900 1920 1940 1960 1980 2000Figure 1.3 Uptake of antenatal care by women in England and Walespatchily applied provision of complex tests, whose availabilityoften depends as much on the whims of a health authority’sideas of financial priority as on the needs of the women andtheir fetuses. As well as these economic considerations, doctors planningthe care of women in pregnancy should consider the women’sown wishes. Too often antenatal clinics in the past have beendesignated cattle markets; the wishes of women coming for careshould be sought and paid attention to. A recurrent problem isthe apparent rush of the hospital clinic. The waiting time is asource of harassment and so is the time taken to travel to theclinic. Most women want time and a rapport with the antenataldoctor or midwife to ask questions and have them answered in Figure 1.5 An antenatal clinic in 2001a fashion they can understand. It is here that the midwivescome into their own for they are excellent at the care ofwomen undergoing normal pregnancies. In many parts of the country midwives run their own clinicsin places where women would go as part of daily life. Here,midwives see a group of healthy normal women throughpregnancy with one visit only to the hospital antenatal clinic. Independent Home hospitals and (2.2%) To get the best results, women at higher risk need to be maternity unitsscreened out at or soon after booking. They will receive (0.5%)intensive care at the hospital consultant’s clinic and those atintermediate risk have shared care between the generalpractitioner and the hospital. The women at lower risk are seenby the midwives at the community clinics. Programmes of thisnature now run but depend on laying down protocols for careagreed by all the obstetricians, general practitioners andmidwives. Co-operation and agreement between the threegroups of carers, with mutual respect and acceptance of eachother’s roles, are essential. Janet Campbell started something in 1920. We should notnecessarily think that the pattern she derived is fixed forever,and in the new century we may start to get it right for thecurrent generation of women. NHS hospitals (97.3%)Styles of antenatal careThe type of antenatal care that a woman and her generalpractitioner plan will vary with local arrangements. Theimportant first decision on which antenatal care depends is Figure 1.6 Place of birth in England and Wales, 19982
  8. 8. Organisation of antenatal carewhere the baby will be delivered. Ninety seven per cent ofbabies in the UK are now delivered in institutions, a third ofthe 2.2% of domiciliary deliveries are unplanned, so about Box 1.1 Fees paid to GPs on the obstetrics list for1.5% are booked as home deliveries. If the delivery is to be in maternity services April 1997an institution there is still the choice in some areas of general £practitioner deliveries either at a separate unit run by general Complete maternity medical services 186practitioners isolated from the hospital or in a combined unit Antenatal care only from before 16 weeks 100with a consultant. Most deliveries take place in an NHS hospital Confinement 42under the care of a consultant team. A small but possibly Postnatal care only 42increasing number in the next few years may be delivered inprivate care, by a general practitioner obstetrician, a consultantobstetrician, or an independent midwife. Recently a series ofmidwife led delivery units have been established with noresidential medical cover. Once the plans for delivery are decided, the pattern ofantenatal visits can be worked out. If general practitioners ormidwives are going to look after delivery, antenatal care mightbe entirely in their hands, with the use of the local obstetric NHS consultant clinicsunit for investigations and consultation. At the other end of the Midwife only clinics Midwife domiciliary visitsspectrum, antenatal care is in the hands of the hospital unitunder a consultant obstetrician and a team of doctors andmidwives, the general practitioner seeing little of the woman 3until she has been discharged from hospital after delivery. Most women, however, elect for antenatal care betweenthese two extremes. They often wish to take a bigger part in Millionstheir own care. In some antenatal clinics the dipstick test forproteinuria is done by the woman herself. As well as providingsome satisfaction, this reduces the load and waiting time at theformal antenatal visit. 2 During pregnancy there may be visits, at certain agreedstages of gestation, to the hospital antenatal clinic for crucialchecks, and for the rest of the time antenatal care is performedin the general practitioner’s surgery or midwives’ clinic. Thesepatterns of care keep the practitioner involved in the obstetriccare of the woman and allow the woman to be seen in slightlymore familiar surroundings and more swiftly. In some areas 1clinics outside the hospital are run by community midwives;these are becoming increasingly popular. Home antenatal carevisits also take place, including the initial booking visit. Delivery may be in the hospital by the consultant led team,by a general practitioner obstetrician, or by a midwife. It is wise,with the introduction of Crown indemnity, that all generalpractitioner obstetricians have honorary contracts with the 1957 1967 1977 1987 1997hospital obstetric department that they attend to supervise or Figure 1.7 Outpatients attendances at antenatal clinics in millions, 1957–97perform deliveries. About 2% of women now have a homedelivery. More than half of these are planned and for thisgroup, antenatal care may well be midwifery led (see ABC ofLabour Care).Early diagnosis of pregnancyWhen a woman attends a practitioner thinking that she ispregnant, the most common symptoms are not always 2 4 8 12amenorrhoea followed by nausea. Many women, particularly Weeks Weeks Weeks Weeksthe multiparous, have a subtle sensation that they are pregnanta lot earlier than the arrival of the more formal symptoms and Womens awareness ofsigns laid down in textbooks. Traditionally, the doctor may elicit LMP Ovulation being pregnantclinical features, but most now turn to a pregnancy test at the *first hint of pregnancy. Amenorrhoea Symptoms NauseaSymptoms Breast tinglingThe symptoms of early pregnancy are nausea, increased Figure 1.8 Time at which a group of primiparous women first thought thatsensitivity of the breasts and nipples, increased frequency of they were pregnant in relation to the more conventional symptoms. Themicturition, and amenorrhoea. mean ( ) and range are given in weeks of gestation. ____ extremes. 3
  9. 9. ABC of Antenatal CareSigns 100 000The doctor may notice on examination a fullness of the breasts Urinary human chorionic gonadotrophin (IU/24 h)with early changes in pigmentation and Montgomery’stubercuiles in the areola. The uterus will not be felt throughthe abdominal wall until about 12 weeks of pregnancy. Onbimanual assessment uterine enlargement is detectable before 10 000this time while cervical softening and a cystic, generally softfeeling of the uterus can be detected by eight weeks. This moresubtle sign is not often sought as vaginal examination is notusually performed on a normal woman at this time. Lower limit of immunological testsTests 0 10 20 30 40Mostly the diagnosis of pregnancy is confirmed by tests Weeks of gestationchecking for the higher concentrations of human chorionic Last menstrual periodgonadotrophin that occur in every pregnancy. The old Fertilisationbiological tests using rabbits and frogs are now gone and have First missed periodbeen replaced by immunological tests. These depend on the Second missed periodpresence of human chorionic gonadotrophin in the body Figure 1.9 Human chorionic gonadotrophin values rise sharply in earlyfluids, which is reflected in the urine. The more sensitive the gestation but are reduced in the second half of pregnancy. The normaltest, the more likely it is to pick up the hormone at lower range 2 SD is shownconcentrations—that is, earlier in pregnancy. Enzyme linked immunosorbent assay (ELISA) is the basis ofmany of the commercial kits currently available in chemistshops. The assay depends on the double reaction of standardphase antibody with enzyme labelled antibody, which issensitive enough to detect very low concentrations of humanchorionic gonadotrophin. Positive results may be thereforedetectable as early as 10 days after fertilisation—that is, fourdays before the first missed period. Vaginal ultrasound can detect a sac from five weeks and afetal cardiac echo a week or so later (Chapter 4), but this wouldnot be used as a screening pregnancy test.ConclusionAt the end of the preliminary consultation women may askquestions about the pregnancy and the practitioner will dealwith these. Most of these queries will be considered in thechapter on normal antenatal management. For most womenthe onset of pregnancy is a desired and happy event, but for afew it may not be so and practitioners, having established adiagnosis, may find that they are then asked to advise ontermination of pregnancy. This they should do if their views onthe subject allow; if not, they should arrange for one of theirpartners to discuss it with the patient. Most women, however,will be happy to be pregnant and looking forward to a Figure 1.10 Clearview pregnancy test results. The horizontal bar in thesuccessful outcome. top chamber shows that a urine sample has progressed satisfactorily from the lower chamber. A horizontal bar in the middle chamber shows a positive result (right) and its absence a negative result (left)Recommended readingG Cnattingius V. Scientific basis of antenatal care. Cambridge: Antenatal care has evolved from a hospital based service to a Cambridge University Press, 1993. community based service for normal women. Those with aG Cole S, McIlwaine G. The use of risk factors in predicting higher risk of problems are best seen in hospital clinics. consequences of changing patterns of care in pregnancy. In Chamberlain G, Patel N, eds. The future of the maternity services. London: RCOG Press, 1994. The picture of the infant welfare clinic is reproduced by permission ofG Collington V. Antenatal care. London: South Bank University, William Heinemann from University College Hospital and its Medical 1998. School: a History by W R Merrington. The Clearview pregnancy test result is reproduced by permission of Unipath, Bedford.4
  10. 10. 2 The changing body in pregnancyPregnancy is a load causing alterations not just in the mother’s Pregnancy causes physiological and psychological changes,pelvic organs but all over the body. Fetal physiology is different which affect all aspects of the woman’s life.from that of an adult, but it interacts with the mother’s systems,causing adaptation and change of function in her body. Theseadaptations generally move to minimise the stresses imposedand to provide the best environment for the growing fetus; theyare usually interlinked smoothly so that the effects on the 38function of the whole organism are minimised. 36 34 Heart 32 Oxygen consumption (ml/min)Cardiovascular system 30 28 LungThe increased load on the heart in pregnancy is due to greater 26 24 Kidneysneeds for oxygen in the tissues. 22 20 BreastsG The fetal body and organs grow rapidly and its tissues have 18 an even higher oxygen consumption per unit volume than Uterus 16 the mother’s. 14 PlacentaG The hypertrophy of many maternal tissues, not just the 12 breasts and uterus, increases oxygen requirements. 10 8G The mother’s muscular work is increased to move her Fetus 6 increased size and that of the fetus. 4 2 Cardiac output is the product of stroke volume and heart 0rate. It is increased in pregnancy by a rise in pulse rate with a 10 20 30 40small increase in stroke volume. Cardiac muscle hypertrophy Weeks of gestationoccurs so that the heart chambers enlarge and output increasesby 40%; this occurs rapidly in the first half of pregnancy and Figure 2.1 Increase in oxygen consumption during pregnancy. A major part of the increase goes to the products of conception (fetus andsteadies off in the second. In the second stage of labour, cardiac placenta)output is further increased, with uterine contractions increasingoutput by a further 30% at the height of the mother’s pushing. During pregnancy the heart is enlarged and pushed up bythe growing mass under the diaphragm. The aorta is unfoldedand so the heart is rotated upwards and outwards. Thisproduces electrocardiographic and radiographic changeswhich, although normal for pregnancy, may be interpreted asabnormal if a cardiologist or radiologist is not told of thepregnancy. Cardiac output (l/min) 6 Blood pressure may be reduced in mid-pregnancy, but pulsepressure is increased and peripheral resistance generallydecreases during late pregnancy. 120 4Blood pressure (mm Hg) 100 0 80 0 10 20 30 40 Weeks of gestation Figure 2.2 Cardiac output in pregnancy. The increase occurs very early 60 and flattens from 20 weeks 40 12 16 20 24 28 32 36 40 pregnant Box 2.1 Changes in the ECG in normal pregnancy Weeks of gestation Non- • Deep Q waves in I and II • T wave flattened or inverted in IIIFigure 2.3 Systolic and diastolic blood pressures during pregnancy. The • ST segment depressedmid-trimester dip found in some women is seen more in the diastolic • Extra-systolies frequentthan in the systolic pressure 5
  11. 11. ABC of Antenatal Care Maternal blood volume increases, the changes in plasma 100 non-pregnant values (%) Blood volumevolume being proportionally greater than the increase in red 80 Increase abovecell bulk. Hence haemodilution occurs; this used to be called a Plasma volume Deliveryphysiological anaemia, a bad phrase as it is paradoxical to have Red cell mass 60a physiological pathological process. 40 The heart sounds are changed. 20G A systolic ejection murmur is common.G A third cardiac sound is commonly heard accompanying 0 12 28 32 36 40 ventricular filling. Weeks of gestation The electrical activity of the heart on an electrocardiogram Figure 2.4 Increase in blood volume and its components in pregnancychanges.G The ventricles become hypertrophied, the left to a greater extent than the right and therefore left ventricular preponderance is seen in the QRS deviation. Heart valves and chamber volumes may change during Non-pregnant Latepregnancy. The heart becomes more horizontal so 4000 state pregnancycardiothoracic ratio is increased and it has a straighter upper Inspiratory capacity Inspiratoryleft border. These changes can be visualised by cross-sectional reserve 3000echocardiography, which depends on the reflection of highfrequency sound from inside the heart. Vital capacity Volume (ml) 2000 reserve volume Residual Expiratory TidalRespiratory system 1000 Functional residual Box 2.2 Changes in chest radiographs in normal pregnancy Inspiration capacity 0 Lungs volume Expiration • Show increased vascular soft tissue • Often have a small pleural effusion especially straight after 1000 delivery The most common changes seen on chest x ray films are Figure 2.5 Changes in inspiratory and expiratory volumes in pregnancyshown in the box. Always ensure that the radiology departmentis told on the request form that a woman is pregnant and givean approximate stage of gestation. Only when there are strongindications should chest radiography be performed inpregnancy at all and then full radiological shielding of theabdomen must be used. 200 Glomerular filtration In early pregnancy women breathe more deeply but notmore frequently under the influence of progesterone. Hence rate (ml/min)alveolar ventilation is increased by as much as a half above 150prepregnant values so that pO2 levels rise and carbon dioxide isrelatively washed out of the body. Later the growing uterus increases intra-abdominal pressure 100so that the diaphragm is pushed up and the lower ribs flareout. Expiratory reserve volume is decreased but the vital 50capacity is maintained by a slight increase in inspiratorycapacity because of an enlarged tidal volume. This may lead to 0 8 16 24 32 40a temporary sensation of breathlessness. Explanation usually Weeks of gestationreassures the woman. 1000 900 Renal blood flowUrinary system 800 (ml/min)Changes in clearanceRenal blood flow is increased during early pregnancy by 40%. 700The increase in glomerular filtration rate is accompanied by 600enhanced tubular reabsorption; plasma concentrations of ureaand creatinine decrease. 500 The muscle of the bladder is relaxed because of increasedcirculating progesterone. Increased frequency of micturition 0 8 16 24 32 40due to increased urine production is a feature of early Figure 2.6 Changes in the glomerular filtration rate and in renal bloodpregnancy. Later the bladder is mechanically pressed on by the flow in pregnancy6
  12. 12. The changing body in pregnancygrowing uterus and the same symptoms occur but for adifferent reason. The muscle walls of the ureters are relaxed by progesteroneso that the ureters become larger, wider, and of lower tone.Sometimes stasis occurs in the ureters; therefore proliferationof bacteria and the development of urinary infection is morelikely to occur.Endocrine systemAll the maternal endocrine organs are altered in pregnancy,largely because of the increased secretion of trophic hormones Figure 2.7 Changes in the ureters in pregnancy, during which theyfrom the pituitary gland and the placenta. lengthen and become more tortuous and dilatedPituitary glandThe pituitary gland is increased in size during pregnancy,mostly because of changes in the anterior lobe.Anterior lobeG Prolactin. Within a few days of conception the rate of prolactin production increases. Concentrations rise until Hypothalamus Neurosecretory term following the direct stimulation of the lactotrophs by cells oestrogens. Human placental lactogen, which shows shared biological activity, exerts an inhibitory feedback effect. Prolactin affects water transfer across the placenta and therefore fetal electrolyte and water balance. It is later concerned with the production of milk, both initiating and maintaining milk secretion.G Gonadotrophins. The secretions of both follicular stimulating hormone and luteinising hormone are inhibited during Venal portal pregnancy. systemG Growth hormone. The secretion of growth hormone is Hypophyseal inhibited during pregnancy, probably by human placental artery lactogen. Metabolism in the acidophil cells returns to normal within a few weeks after delivery and is unaffected by lactation. AnteriorG Adrenocorticotrophic hormone concentration increases slightly in lobe Posterior pregnancy despite the rise in cortisol concentrations. The lobe normal feedback mechanism seems to be inhibited secondary to a rise in binding globulin concentrations.G Thyrotrophin secretion seems to be the same as that in non-pregnant women. The main changes in thyroid activity Hypophyseal Pars in pregnancy come from non-pituitary influences. intermedia vein Figure 2.8 Pituitary gland showing secreting areasPosterior lobeThere are increases in the release of hormones from theposterior pituitary gland at various times during pregnancy andlactation. These, however, are produced in the hypothalamus,carried to the pituitary gland in the portal venous system, andstored there. The most important is oxytocin, which is released 180in pulses from the pituitary gland during labour to stimulate Prolactin (ng/ml)uterine contractions. Its secretion may also be stimulated by 140stretching of the lower genital tract. Oxytocin is also releasedduring suckling and is an important part of the let down reflex. 100 60 Non-pregnantThyroid gland 20Pregnancy is a hyperdynamic state and so the clinical featuresof hyperthyroidism may sometimes be seen. The basal 0 4 8 12 16 20 24 28 32 36 40metabolic rate is raised and the concentrations of thyroid Weeks of gestationhormone in the blood are increased, but thyroid function is Figure 2.9 Changes in prolactin concentrations in pregnancyessentially normal in pregnancy. (means and SEMs) 7
  13. 13. ABC of Antenatal Care In pregnancy the renal clearance of iodine is greatly Thyrotrophin releasingincreased but thyroid clearance also rises so absolute iodine hormone (stimulatory ) Somatostatinlevels remain in the normal range. The raised hCG levels are Hypothalamus (inhibitory )associated with a reduced (inside the normal range) TSH; hCGprobably stimulates the gland in early pregnancy and is capableof stimulating TSH receptors. Tri-iodothyronine and thyroxine (stimulatory )Adrenal glandThe adrenal cortex synthesises cortisol from cholesterol. In Anteriorpregnancy there is an increase in adrenocorticotrophic pituitary Thyroidhormone concentration along with an increase in total plasma stimulatingcortisol concentration because of raised binding globulin hormoneconcentrations. The cortex also secretes an increased amountof renin, possibly because of the increased oestrogenconcentrations. This enzyme produces angiotensin I, which isassociated with maintaining blood pressure. Some renin also Thyroidcomes from the uterus and the chorion, which together stimulatingproduce a large increase in renin concentrations in the first 12 hormoneweeks of gestation. There is little change in Tri-iodothyronine (stimulatory )deoxycorticosterone concentrations despite the swings in and thyroxine (inhibitory )electrolyte balance in pregnancy. The adrenal medulla secretes adrenaline andnoradrenaline. The metabolism seems to be the same duringpregnancy as before; the concentrations of both hormones rise Thyroidin labour. glandPlacenta Figure 2.10 Control of thyroxine secretion in pregnancyThe oestrogen, progesterone, and cortisol endocrine functionsof the placenta are well known. In addition, many otherhormones are produced with functions related to maternaladaptation to the changes of fetal growth. In some susceptible women, progesterones may softencritical ligaments so that joints are less well protected and may 700 Uterine blood flowseparate (e.g. separation of the pubic bones at the symphysis). (ml/min) 500 300Genital tractThe uterus changes in pregnancy; the increase in bulk is due 100mainly to hypertrophy of the myometrial cells, which do not 0increase much in number but grow much larger. Oestrogens 0 8 16 24 32 40stimulate growth, and the stretching caused by the growing Weeks of gestationfetus and the volume of liquor provides an added stimulus to Figure 2.11 Changes in uterine blood flow in pregnancyhypertrophy. The blood supply through the uterine and ovarian arteriesis greatly increased so that at term 1.0–1.5 l of blood areperfused every minute. The placental site has a preferentialblood supply, about 85% of the total uterine blood flow goingto the placental bed. The wide range of normal physiological changes of gestation must be allowed for when making clinical diagnoses about The cervix, which is made mostly of connective tissue, diseases in pregnancy.becomes softer after the effect of oestrogen on the groundsubstance of connective tissue encourages an accumulation ofwater. The ligaments supporting the uterus are similarlystretched and thickened.Recommended readingG Chamberlain G, Broughton-Pipkin F, eds. Clinical physiology in The figure showing the control of thyroid secretion is reproduced by obstetrics. 3rd edn. Oxford: Blackwell Scientific Publications, permission of Blackwell Scientific Publications from Clinical Physiology 1998. in Obstetrics edited by F Hytten and G Chamberlain. The figureG de Sweit M, Chamberlain G, Bennett M. Basic science in obstetrics showing prolactin secretion during pregnancy is reproduced by and gynaecology. 3rd edn. London: Harper and Bruce, 2001. permission of the American Journal of Obstetrics and Gynecology (Rigg LA, Lein A, Yen SCC, 1977;129:454–6).8
  14. 14. 3 Normal antenatal managementAntenatal care has six functions (see Box 3.1). The first two arethe same as any performed in an outpatient clinic (treatmentof symptoms); the second two relate to multiphasic screening,of which antenatal care was an early example; the third pair arepart of health education. Box 3.1 Aims of antenatal care • Management of maternal symptomatic problems Booking visit • Management of fetal symptomatic problems • Screening for and prevention of fetal problems Ultrasound scan • Screening for and prevention of maternal problems • Preparation of the couple for childbirth • Preparation of the couple for childrearing Conventional care Antenatal care in the UK is performed by a range ofprofessionals: midwives, general practitioners, and hospitaldoctors. In many areas up to 90% of antenatal care is in the Minimal carehands of general practitioners and community midwives. Inmany parts of the country midwives hold their own clinicsoutside the hospital or visit women at home. Probably thoseinitially at lower risk do not need routine specialist visits for Minimalist carethey offer little or no benefit. Many women now carry their ownnotes, which leads to greater understanding of what is going on. In the UK many women book for antenatal care by 14 weeks 12 16 20 24 28 32 36 40 44and are seen at intervals. There is no association between the Weeks of gestationnumber of visits and outcome; in Switzerland there are an Figure 3.1 Intervals of antenatal visits: conventional pattern (top); currentaverage of five and in The Netherlands as many as 14, but ideas of low risk care (middle); plan for the least number of visitsoutcomes are the same. The number of visits depends on a (bottom)traditional pattern laid down by Dame Janet Campbell in the1920s (Chapter 1) rather than on being planned withthoughts relating to the contemporary scene. In an idealworld, the follow-up antenatal visits would be plannedindividually according to the needs of the woman andassessment of her risk. A more rational plan of care of normal primigravidas and Table 3.1 Care for normal multi- and primigravidasmultigravidas is laid down in Table 3.1. With these criteria, Week ofantenatal care would be more cost effective and no less clinically gestation Main purpose of visit*useful. When pioneers have tried to reduce the number of visitsfrom the traditional number, however, there has been resistance Minimum care for normal multigravidasfrom older obstetricians, conventional midwives, women having 12 History and examination, clarification of uncertain gestation, identification of risk factors for antenatalbabies, and their mothers, all of whom think that Campbell’s by care and confinement, booking blood tests, bookingnow traditional pattern must be right. A randomised controlled scan in some unitstrial in south-east London actually found women in the fewer Advice on diet, drugs, work, and exercisevisits group were more likely to be dissatisfied although 15–20 Downs serum screening, Fetoprotein, anomalyoutcomes of the groups were the same. ultrasound scan As well as the clinical regimen, antenatal care now entails a 22 Fundal height, baseline weightwhole series of special tests, but these are not generally used for 30 Fundal height, weight gain, identification of intrauterine growth restriction andthe normal pregnant population. pre-eclampsia 36 Fundal height, weight gain, identification of malpresentationPrepregnancy care 40 Assessment if need for induction Additional visits for normal primigravidasSome aspects of a couple’s way of life may be checked before 26 Blood pressure, urine analysis, discussion of deliverypregnancy. The man and the woman’s medical and social and infant feedinghistory, and, if relevant, her obstetric career can be assessed. 34 Blood pressure, urine analysis, discussion of deliveryImmunity from infections such as rubella can be tested; and infant feedingalternative treatments to some longstanding conditions such as 38 Blood pressure, urine analysis, discussion of deliveryulcerative colitis can be discussed. The possibility of a and infant feeding 41 Blood pressure, urine analysis, discussion of deliveryrecurrence of pre-existing problems such as deep vein and infant feedingthrombosis can be assessed. Dietary habits and problems at * Blood pressure reading and urine analysis are performed at everywork can be assessed and changes in consumption of cigarettes visit.or alcohol may be considered. Once pregnancy has started the 9
  15. 15. ABC of Antenatal Carecouple have only two options—that is, to continue or stop thepregnancy. Prepregnancy care allows more time for the Box 3.2 Aims of prepregnancy carecorrection of detectable problems and the prevention of their • To bring the woman to pregnancy in the best possible healthrepetition—for example, giving supplementary folate to women • To attend to preventable factors before pregnancy starts—for example, rubella inoculationwhose children have abnormalities of the central nervous • To discuss diabetes and aim for excellent glycaemic controlsystem. It is now recommended that extra folate is started by all • To assess epileptic medication in terms of fit control andwomen before pregnancy to avoid deficiency in very early teratogenicitypregnancy when the fetal neural tube is closing (21–28 days of • To discuss antenatal diagnoses and management of abnormalityfetal life) so as to reduce the risk of spina bifida. • To give advice about the effects of: • pre-existing disease on the pregnancy and unborn child • the pregnancy on pre-existing disease and its management • To consider the effects of recurrence of events from previous pregnanciesBooking visit • To discuss the use of prophylactic folate before conceptionOnce pregnancy has been diagnosed, the woman usually booksa visit at the antenatal clinic, the GP surgery or at home with themidwife who will lead in antenatal care. This is the longest butmost important visit. It used to take place at 8–12 weeks’gestation, but in many clinics it has moved to 12–14 weeks. The APRILwoman’s medical state is assessed so that the current pregnancy 5 10 15 20 2 AR 26 31 5 3can be placed into the appropriate part of a risk spectrum. M 16 21 0 5 10 M AY 11Baseline data are essential at this point and are obtained from 6 15 20 1the history, an examination, and relevant investigations. 24 25 30 19 B FE 14 4History 40 9 JU 9 GES NESymptoms that have arisen in the current pregnancy before the 14 O F 4 RI O TAT 19 D PE AY 30booking visit are ascertained—for example, vaginal bleeding ION TE 24 ST T D 25 RM PERand low abdominal pain. 36 4 LA RS 29 15 20 IOD FI JAN 4 IN WG Menstrual history. To assess the expected date of delivery 9 EEK 10 details are needed about the last normal menstrual period S 14 19 JULY 32 8 5 including its date, the degree of certainty of that date, and 26 31 24 whether cycles are reasonably regular around 28 days. The 29 21 use of oral contraception or ovulation induction agents that 28 12 3 16 might inhibit or stimulate ovulation should be discussed. A GESTATION C DE 8 11 CALCULATOR firm date for delivery from the last menstrual period can be 13 6 24 16 AU 18 1 obtained from about 80% of women. G 20 23 26 28G From this calculate the expected date of delivery with a 21 16 2 7 calculator. Do not do sums in the head; this can cause V NO 11 6 17 12 1 trouble when a pregnancy runs over the end of a year. A 27 22 SE 27 12 17 22 7 2 PT woman can be told that she has an 85% chance of delivering OCT within a week of the expected date of delivery, but we must emphasise at this point that this date is only a mathematical Figure 3.2 An adjustable obstetric calculator should always be used to calculate the current stage of gestation and the expected date of delivery probability and, as with other odds, the favourite does not always win the race. Most units now rely on ultrasound to confirm gestation and alter the EDD if the scan date varies considerably, i.e. more than 10 days difference.G Medical history. Specific illnesses and operations of the past should be inquired about, particularly those that entail treatment that needs to be continued in pregnancy—for example, epilepsy and diabetes.G Family history. There may be conditions among first degree relatives (parents or siblings) that may be reflected in the 30 current pregnancy, such as diabetes or twinning. Spontaneous 25G Sociobiological background. Age, parity, social class, and race of Induced Frequency (%) the woman all affect the outcome of the pregnancy. Smoking 20 and alcohol consumption also affect the outcome. Socioeconomic class is usually derived from the occupation 15 of the woman or her partner. It reflects the influence of a mixed group of factors such as nutrition in early life, diseases 10 in childhood, education, and past medical care. It also 5 correlates with potential birth weight, congenital abnormality rates, and eventually perinatal mortality. Less strongly 0 associated are preterm labour and problems in care of the 30 32 34 36 38 40 42 44 46 newborn. Weeks of gestationG Obstetric history. The woman’s obstetric history should be Figure 3.3 Distribution of length of gestation for spontaneous and discussed carefully as it contains some of the best markers for induced single births when the last menstrual period is known (n 16 000)10
  16. 16. Normal antenatal management performance in the current pregnancy. If the woman has Table 3.2 Proportions of live births in each socioeconomic had a previous miscarriage or termination of pregnancy, the class in England and Wales adjusted by job description of doctor should ask about the stage of gestation, and any husband or partner (1998) illness afterwards. Of babies born, the progress of the pregnancy, labour, and puerperium are needed and the stage Population of gestation and birth weight of the infant. Intrauterine having Job babies growth restriction and preterm labour may be recurrent and Social class description (%) should be inquired about in previous pregnancies. The terms gravidity and parity are often applied to women in I II Professional & supervisory 25.6 pregnancy. Gravidity refers to pregnancy, so anyone who is IIINM Skilled, non-manual 6.7 IIIM Skilled, manual 16.6 gravid is or has been pregnant. A woman who is pregnant for IV V Semiskilled & unskilled 10.3 the first time is a primigravida. Parity refers to having given Not classifiable* 3.0 birth to a viable liveborn or a stillborn child. Not married 37.8 * In many surveys unemployed people are classified by their last occupation if they had one.ExaminationA brief but relevant physical examination should be performed.The woman’s height is important as it correlates loosely withpelvic size, but shoe size is a poorer predictor. Weight is lessoften monitored in pregnancy these days, but a booking weightwill enable a Body Mass Index (BMI) to be measured. This isthe weight in kilograms divided by the height squared (weight(kg)/height (cm2)). BMI is useful in determining those atincreased risk during pregnancy (over 30) who requireconsultant obstetric care. A value of over 39 (morbidly obese)may indicate that an anaesthetic assessment is necessary toassess potential problems in labour at delivery. The clinical G0 P0presence of anaemia should be checked and a briefexamination of the teeth included, if only to warn the womanto visit a dentist. Tooth and gum deterioration may be rapid inpregnancy and dental care is free at this time and for a yearafter delivery. Check whether the thyroid gland is enlarged. The blood G1 P0pressure is taken, preferably with the woman resting for a fewminutes before. The spine should be checked for any tenderareas as well as for longer term kyphosis and scoliosis, whichmight have affected pelvic development; the legs should beexamined for oedema and varicose veins. The abdomen is inspected for scars of previous + G2 P1operations—look carefully for laparoscopy scars below theumbilicus and for a Pfannenstiel incision above thepubis. Palpation is performed for masses other thanthe uterus—for example, fibroids and ovarian cysts. If thebooking visit is before 12 weeks the uterus probably will not befelt on abdominal examination, but in a multiparous + + G2 P2woman it may be; this should not cause the examiner to makeany unnecessary comments about an enlarged uterus at thisstage. A vaginal assessment was traditionally performed at thebooking visit. Its function was to confirm the soft enlargement + + G3 P2of the uterus in pregnancy, to try to assess the stage ofgestation, to exclude other pelvic masses, and to assess the bonypelvis. Many obstetricians now do not do a pelvic assessment atthis stage; no woman likes having a vaginal examination and, if Figure 3.4 Gravidity (G) and parity (P)done in early pregnancy, it is associated in the woman’s mindwith any spontaneous miscarriage which may occursubsequently, even though this is irrelevant to the examination.Fetal size will soon be checked by ultrasound. Even assessmentof the bony pelvis in late pregnancy may not be required as thefetal presenting part is available for check against the inletwhile the effect of progesterone on the pelvic ligaments isat its maximum. By this time the woman has moreconfidence in the antenatal staff and is more willing to have avaginal examination. If the head is engaged, this is a goodmeasure of pelvis size. If it is not, a vaginal assessment may stillbe needed. 11
  17. 17. ABC of Antenatal CareInvestigationsA venous blood sample is checked for:G Haemoglobin concentration or mean cell volume (see Chapter 8).G ABO and rhesus groups and, if relevant, rhesus antibodies. laparoscopy The former is to allow swifter cross-matching of blood if needed in pregnancy or labour; the latter is to warn of problems and be a baseline if a rhesus-positive fetus is in the uterus of a rhesus-negative woman.G Antibodies to other blood groups—for example, Kell, to give pfannens warning of potential incompatibility with the fetus in the presence of less common blood groups.G Haemoglobinopathies in women originating from Mediterranean, African, and West Indian countries.G Syphilis. A Wassermann reaction (WR) is non-specific; most Figure 3.5 Laparoscopy and Pfannenstiel scars clinics now use the Treponema pallidum haemagglutination test to investigate more specifically, but no test can be expected to differentiate syphilis from yaws or other Non-pregnant 8 weeks 10 weeks treponematoses.G Rubella antibodies.G HIV antibodies. If the woman is at risk of infection through intravenous drug misuse, having received contaminated blood transfusions, coming from parts of the world with a high HIV rate (e.g. sub-Saharan Africa), or having a partner who is HIV positive, she may request or be advised to have an HIV test. Full counselling should include her understanding the implications of both having the test and any positive result. In some parts of the UK, antenatal testing is offered to all with a Figure 3.6 Relative growth of uterus in early pregnancy. Growth is usually modified advice service beforehand. The mother can opt out. in width rather than length, so the uterus seems fuller at first. It is alsoG Hepatitis B antibodies. softer and has a cystic qualityG Toxoplasmosis antibodies (if clinically appropriate).G Cytomegalic virus antibodies (if clinically appropriate).Later blood checks are for:G Fetoprotein level analysis for abnormality of the central nervous system.G Down’s syndrome serum screening by double or triple test.The urine is checked for: 36G Protein, glucose and bacteria.Chest radiographs are rarely taken except in women from partsof the world where pulmonary tuberculosis is still endemic. An ultrasound assessment is now performed on mostpregnant women in the UK. It is best done at about 22 12 Figure 3.7 Size of uterus at various stages of gestation in pregnancyFigure 3.8 Ultrasound of fetal head showing the midline echo, thebiparietal diameter of the head circumference outline12
  18. 18. Normal antenatal management18–20 weeks to measure the biparietal diameter and so get abaseline value of fetal size and confirmation of the stage ofgestation to firm up the expected date of delivery. Grosscongenital abnormalities may be found (Chapter 4). Ultrasound between 10 and 13 weeks can measure nuchaltranslucency, which is being evaluated as a screening test forDown’s syndrome (Chapter 4). At 18 weeks congenitalabnormalities such as spina bifida, omphalocele, and abnormalkidneys may be excluded. A four chamber view of the heart isalso possible at this stage to exclude gross abnormalities, butdetails of cardiac connections may not be obvious until 22–24weeks. Other conditions which are characterised by decreasedgrowth such as microcephaly or some forms of dwarfism may First sacral vertebraalso not be apparent until late in the second trimester. Hence, though 16–18 weeks would be a useful time to assessgestational age by ultrasound, much later assessments areneeded to assess fetal normality. In addition, more highlyskilled ultrasonographers and equipment of high resolution areneeded to produce scans to enable assessment of normality.Many of these ultrasound studies of fetal anatomy have beendeveloped in specialist units with highly skilled obstetric 13 cmultrasonographers. The ordinary ultrasound service at a districtgeneral hospital cannot be expected always to provide such skill 11 cmor equipment, although with increased training and bettermachines, some centres are now providing a fuller exclusionservice at 20–24 weeks’ gestation. Also at 24 weeks Doppler flow A Symphysis pubismm100 90 80 70 First sacral vertebra 60 50 Greater sciatic notch 40 30 B.P.D (mm) 20 Fifth sacral vertebra 0 Symphysis pubis 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40Figure 3.9 Mean ( 2 SD) biparietal diameter of the fetal head in anormal population. Note the narrow range of normal values in earlier B 55-60°pregnancy, a great difference from that of biochemical test results 40 Inferior ramusSymphysiofundal height (cm) 35 of pubis 13 cm 30 11 cm 25 Sacro tuberous ligament 20 20 22 24 26 28 30 32 34 36 38 40 Sacrum Weeks of gestation CFigure 3.10 Mean ( SD) of symphysio-fundal height by weeks ofgestation. Note the wide range of readings for any given week of gestation Figure 3.11 Outline of the normal bony pelvis. (A) Inlet seen from above.and the even wider range of expected gestation weeks for any given (B) Side view showing angle of inclination of the pelvic nm. (C) Outletreading seen from below 13